Yep - all the focus on the engineering specifics here seems to miss the sheer magnitude of the thing. Knight risked 4x their annual revenue in under an hour! You can get away with some incredibly crappy systems if you have final-line safeguards like "let's not risk all the money we've ever seen and more without asking a human".
The team of MBAs might screw up an Excel formula and lose money on a deal, but presumably if the math comes out to "let's pay $500 billion for Yahoo", somebody's going sanity-check that before they transfer the money.
I think companies have on occasion lost billions due to a glitch in a contract, sometimes due to delegating work to a novice who didn't fully understand it. And a contract is not totally unlike a program.
The team of MBAs might screw up an Excel formula and lose money on a deal, but presumably if the math comes out to "let's pay $500 billion for Yahoo", somebody's going sanity-check that before they transfer the money.